1. Field of the Invention
The present invention relates to a polylactic acid composite material and a molded body using the same.
2. Related Background Art
Polylactic acids show so-called biodegradability, i. e., the property of being broken down by the action of microorganisms and enzymes, and the decomposition products of polylactic acids are lactic acid, carbon dioxide and water, which are harmless to the human body. Accordingly, polylactic acids have attracted attention as medical materials and as substitutes for all-purpose resins.
Polylactic acids are crystalline resins; however, the crystallization rate of these resins is slow, and polylactic acids actually show behavior that is close to that of amorphous resins. Specifically, since such resins show abrupt and extreme softening (ordinarily, to an elastic modulus of less than 1/100) in the vicinity of the glass transition temperature, it is difficult to obtain sufficient characteristics in terms of heat resistance, moldability, mold release properties, impact resistance and the like.
Accordingly, various methods for imparting the abovementioned characteristics have been proposed in order to ameliorate such problems. For example, a method in which moldability is imparted by adding higher fatty acid bis-amides to polylactic acids so that blocking is prevented is disclosed in Japanese Patent Application Laid-Open No. H6-299054, a method in which mold release properties and molding workability are imparted by adding fatty acid amides to a thermoplastic polymer composition consisting chiefly of a polylactic acid is disclosed in Japanese Patent Application Laid-Open No. H8-27363, and a method in which the degradation rate is controlled by adding aliphatic carboxy acid amides or the like to a polymer consisting chiefly of a polylactic acid is disclosed in Japanese Patent Application Laid-Open No. H8-183898.
Furthermore, a method in which a molded body that possesses both transparency and heat resistance (crystallinity) is obtained by adding a transparent nucleus agent such as an aliphatic carboxylic acid amide or the like to an aliphatic polyester such as a polylactic acid or the like is described in Japanese Patent Application Laid-Open No. H9-278991.